A clean room in which semiconductor manufacturing apparatuses are installed is supplied with a clean air which has controlled temperature and humidity and from which dusts are removed. Generally, semiconductor manufacturing apparatuses generate heat during operation, or generates various kinds of gas containing a toxic gas. For this reason, each of various semiconductor manufacturing apparatuses installed in a clean room is separately accommodated in a housing, and the air which circulated through an interior of the housing is directly exhausted out of the clean room through a duct or exhausted out of the clean room after removing a harmful gas (harmful component).
That is, the air in the clean room is introduced into the housing of the semiconductor manufacturing apparatus installed in the clean room. The air, which is warmed during circulation in the housing or in which a gas is mixed, is exhausted directly to outside the clean room.
Therefore, since all the air introduced into the clean room installed in the housing of the semiconductor manufacturing apparatus is exhausted out of the clean room, an amount of air corresponding to the amount of air exhausted from each semiconductor manufacturing apparatus must be produced and supplied to the clean room. The air supplied to the clean room is air which has been purified by a HEPA filter or the like, and has accurately controlled temperature and humidity.
An extremely large cost is required for manufacturing the air supplied to the clean room. That is, a running cost of a blower for moving air so as to purify outside air by passing through a filter, and an air-conditioning cost for cooling and heating air so as to control temperature and humidity are required.
As mentioned above, in an air-conditioning system of semiconductor manufacturing apparatuses in a conventional clean room, the costly air supplied to the clean room was exhausted out of the clean room through each semiconductor manufacturing apparatus. Thus, a clean air of which temperature and humidity are controlled was supplied to the clean room. The manufacturing cost of such an air newly supplied the clean room was a large factor which raises the running cost of a clean room.